Processes are needed for the thermal recovery of petroleum crude oil from deposits of sand and shale that lie on or near the earth's surface in many parts of the world.
The true amount of reserves located throughout the world is not known. However, it is estimated that there are at least 30 billion barrels within tar sand and oil shale deposits in the United States alone. These reserves remain as yet un-tapped sources of valuable crude oil that does not require drilling and deep well recovery techniques. Petroleum laden sand and shale deposits are generally positioned on or near the surface of the ground and lay in horizontal layers or shelves that can be exposed, surface mined and processed with any number of available machines. Some deposits require that overburden be removed before mining, others have very little overburden. Some deposits also include levels or strata of green shale and white shale that lie between the petroleum layers. These layers must be mined and removed to access the tar sands and oil shale.
There are a number of different devices, systems and processes that have been developed over the years to process the tar sands and shale by mining the material and then extracting the crude oil or by in-situ extraction to strip and capture the petroleum crude. Some of these processes are operating today as commercially viable enterprises.
Systems that have been developed and used are hot water extraction, solvent extraction, gasification and condensation extraction. Variations on these techniques have been explored. In recent years however, new technologies have been created that permit the use of better, more efficient heating and handling techniques for the sand and shale along with liquid post recovery treatment systems that further process the extracted crude to enhance refining and remove certain undesirable constituents such as sulphur and nitrogen, therefore increasing the value of the preprocessed crude oil.
Needs exist for improved methods for the thermal recovery of petroleum crude oil from deposits of sand and shale.